Tilting mechanisms for the seat of a chair are well known. Typically, such mechanisms allow only rearward tilting and employ an adjustable spring-like mechanism to return the seat to a generally horizontal position when the chair is not in use. Chairs such as these are in common use and have the advantage, over rigid chairs, that the occupant may shift his position in order to transfer the pressure of sitting from one part of his anatomy to another. This shifting is found to be relaxing and aids in postponing or even preventing tension and fatigue.
Improvements over one direction tilting are to be found in U.S. Pat. No. 1,678,668 wherein there is disclosed a chair tilting mechanism which tilts forwardly as well as backwardly and in U.S. Pat. No. 1,723,415 wherein there is disclosed a chair tilting mechanism which is capable of a limited lateral rocking or tilting movement.
Further improvements are to be found in omnidirectionally tiltable chair mechanisms which are described in U.S. Pat. Nos. 2,048,148 (Stoll), 4,099,697 (Von Schuckmann), 4,185,803 (Kalvatn), 4,431,157 (Arild) and 4,498,656 (Arild). The Stoll patent discloses a ball joint surrounded by a coil spring which is held in compression between a flange and a seat mounted swivel bearing. A stub shaft extends between the ball and the swivel bearing. As the occupant's weight is shifted on the seat, tilting can occur in any direction. As soon as the lateral thrust force is relieved, the seat will return to its neutral, home position. This mechanism may be interposed between a standard pedestal tube and the chair seat. In the Von Schuckmann patent the omnidirectionally tilting mechanism must be located in a dedicated base. It comprises a ball received in a socket for universal movement with a shaft secured to and extending from the ball-like member. A star-like array of generally radial tension springs are attached to the shaft and yieldably resist deflection of the shaft out of its normal position in all directions. The patented Kalvatn mechanism comprises a pair of concentric rings which are mutually moveable, each about a torsion bar. This universal tilting mechanism may also be mounted between the chair seat and the standard pedestal. Similarly, in each of the Arild patents there is disclosed a tilting mechanism comprising a pair of torsion bar elements mounted upon yokes disposed normally to one another. Again, these mechanisms may be mounted between the seat and the standard pedestal.
All of the known omnidirectionally tiltable chair support structures are of a size and complexity to require extensive modifications to existing chair structures for their incorporation therein.
It is the object of the present invention to provide an improved mechanism, utilizing a flexure member, for supporting a chair seat such that the seat is tiltable and self righting in a full 360 degrees. Optionally, the seat may also be mounted to swivel a full 360 degrees.
It is a further object of the present invention to provide an omnidirectionally tiltable mechanism which may be mounted totally out of sight and which fits completely within a general standard, central tubular column of any chair support.